<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python documentation Index' />
<link rel="first" href="lib.html" title='Python library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="typesnumeric.html" />
<link rel="prev" href="boolean.html" />
<link rel="parent" href="types.html" />
<link rel="next" href="typesnumeric.html" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name='aesop' content='information' />
<title>3.3 Comparisons </title>
</head>
<body>
<div class="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="3.2 boolean Operations "
  href="boolean.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="3. built-in Types"
  href="types.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="3.4 numeric Types "
  href="typesnumeric.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="boolean.html">3.2 Boolean Operations </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="types.html">3. Built-in Types</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="typesnumeric.html">3.4 Numeric Types </a>
</div>
<hr /></div>
</div>
<!--End of Navigation Panel-->

<h1><a name="SECTION005300000000000000000"></a><a name="comparisons"></a>
<br>
3.3 Comparisons 
</h1>

<p>
Comparison operations are supported by all objects.  They all have the
same priority (which is higher than that of the Boolean operations).
Comparisons can be chained arbitrarily; for example, <code><var>x</var> &lt;
<var>y</var> &lt;= <var>z</var></code> is equivalent to <code><var>x</var> &lt; <var>y</var> and
<var>y</var> &lt;= <var>z</var></code>, except that <var>y</var> is evaluated only once (but
in both cases <var>z</var> is not evaluated at all when <code><var>x</var> &lt;
<var>y</var></code> is found to be false).
<a id='l2h-165' xml:id='l2h-165'></a>
<p>
This table summarizes the comparison operations:

<p>
<div class="center"><table class="realtable">
  <thead>
    <tr>
      <th class="center">Operation</th>
      <th class="left"  >Meaning</th>
      <th class="center">Notes</th>
      </tr>
    </thead>
  <tbody>
    <tr><td class="center" valign="baseline"><code>&lt;</code></td>
        <td class="left"  >strictly less than</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>&lt;=</code></td>
        <td class="left"  >less than or equal</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>&gt;</code></td>
        <td class="left"  >strictly greater than</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>&gt;=</code></td>
        <td class="left"  >greater than or equal</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>==</code></td>
        <td class="left"  >equal</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>!=</code></td>
        <td class="left"  >not equal</td>
        <td class="center">(1)</td></tr>
    <tr><td class="center" valign="baseline"><code>&lt;&gt;</code></td>
        <td class="left"  >not equal</td>
        <td class="center">(1)</td></tr>
    <tr><td class="center" valign="baseline"><code>is</code></td>
        <td class="left"  >object identity</td>
        <td class="center"></td></tr>
    <tr><td class="center" valign="baseline"><code>is not</code></td>
        <td class="left"  >negated object identity</td>
        <td class="center"></td></tr></tbody>
</table></div>
<a id='l2h-166' xml:id='l2h-166'></a><a id='l2h-167' xml:id='l2h-167'></a> <a id='l2h-168' xml:id='l2h-168'></a><a id='l2h-169' xml:id='l2h-169'></a>
<p>
Notes:

<p>
<dl>
<dt><strong>(1)</strong></dt>
<dd><code>&lt;&gt;</code> and <code>!=</code> are alternate spellings for the same operator.
<code>!=</code> is the preferred spelling; <code>&lt;&gt;</code> is obsolescent.

<p>
</dd>
</dl>

<p>
Objects of different types, except different numeric types and different string types, never
compare equal; such objects are ordered consistently but arbitrarily
(so that sorting a heterogeneous array yields a consistent result).
Furthermore, some types (for example, file objects) support only a
degenerate notion of comparison where any two objects of that type are
unequal.  Again, such objects are ordered arbitrarily but
consistently. The <code>&lt;</code>, <code>&lt;=</code>, <code>&gt;</code> and <code>&gt;=</code>
operators will raise a <tt class="exception">TypeError</tt> exception when any operand
is a complex number. 
<a id='l2h-170' xml:id='l2h-170'></a><a id='l2h-171' xml:id='l2h-171'></a>
<p>
Instances of a class normally compare as non-equal unless the class
<a id='l2h-173' xml:id='l2h-173'></a>defines the <tt class="method">__cmp__()</tt> method.  Refer to the
<em class="citetitle"><a
 href="../ref/customization.html"
 title="Python Reference Manual"
 >Python Reference Manual</a></em> for
information on the use of this method to effect object comparisons.

<p>
<strong>Implementation note:</strong> Objects of different types except
numbers are ordered by their type names; objects of the same types
that don't support proper comparison are ordered by their address.

<p>
Two more operations with the same syntactic priority,
"<tt class="samp">in</tt>"<a id='l2h-174' xml:id='l2h-174'></a> and "<tt class="samp">not in</tt>"<a id='l2h-175' xml:id='l2h-175'></a>, are supported
only by sequence types (below).

<p>

<div class="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="3.2 boolean Operations "
  href="boolean.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="3. built-in Types"
  href="types.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="3.4 numeric Types "
  href="typesnumeric.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="boolean.html">3.2 Boolean Operations </a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="types.html">3. Built-in Types</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="typesnumeric.html">3.4 Numeric Types </a>
</div>
</div>
<hr />
<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
</div>
<!--End of Navigation Panel-->
<address>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</address>
</body>
</html>
